Change default BUILDTYPE to Debug

[jfirebaugh]

BUILDTYPE currently defaults to Release, and I frequently find myself forgetting the BUILDTYPE=Debug in BUILDTYPE=Debug make <platform> until halfway through the build.

Since in CI BUILDTYPE will always be explicitly specified, does anyone object to changing the default to Debug for the convenience of running make locally?

[tmpsantos]

I always only build debug.

[mikemorris]

make node doesn't seem to respect this (defaulting to Release still) and requires calling npm install --build-from-source --debug to set BUILDTYPE=Debug through node-pre-gyp...